According to the Shatapatha Brahmana, the Mlecchas speak the languages of the Asuras of Patala.
The gods then cut her off from the Asuras; and having gained possession of her and enveloped her completely in fire, they offered her up as a holocaust, it being an offering of the gods. And in that they offered her with an anuṣṭubh verse, thereby they made her their own; and the Asuras, being deprived of speech, were undone, crying, 'He ’lavaḥ! he ’lavaḥ!'
Such was the unintelligible speech which they then uttered,--and he (who speaks thus) is a Mleccha (barbarian). Hence let no Brahman speak barbarous language [Mleccha languages], since such is the speech of the Asuras. Thus alone he deprives his spiteful enemies of speech; and whosoever knows this, his enemies, being deprived of speech, are undone.
Which Mleccha civilizations and languages speak the languages of the Asuras? Is it Chinese, Arabic, African, etc?
Does any scripture specify which Mleccha languages are revealed by the Asuras?